Powertrain control architectures include systems for monitoring operation of various components and subsystems to ensure proper control and operation, and to identify component and system faults. This includes devices and control algorithms operative to monitor temperatures of some of the components and subsystems. Temperature monitoring can be accomplished using systems having temperature sensing devices, including circuits which utilize thermo-resistive devices, e.g., thermistors and other sensors. These systems and devices for monitoring temperature may have faults which lead to incorrect readings of temperature, and are often required to be monitored.
Monitoring of temperature sensing systems includes systems operative to detect electrical shorts and open circuits. Monitoring can include rationality monitors, wherein a temperature sensor signal is monitored for signal bias or unexpected variations.
One form of rationality monitoring is an algorithm executed in a control module comprising a mathematical model which predicts a temperature based upon operating conditions, and compares the predicted temperature to a temperature measured by the sensing system to determine whether the sensing system is operating properly. This approach requires engineering effort to develop and calibrate the predictive model, and consumes operating space, memory and execution time in the control module.
A risk of executing a temperature rationality monitor includes occurrence of a falsely indicated fault, wherein a system inaccurately identifies presence of a fault, and can be caused by executing the temperature rationality monitor during extreme environmental conditions, or electrical circuit noise, or errors in digital signal processing. One method to address such concerns includes limiting operating conditions as which rationality tests can be conducted, which results in reduced signal resolution, or reduced temperature sensing range.
There is a need for a temperature monitoring scheme which addresses the issues described. Such a system is described hereinafter.